This invention relates to the oil and gas industry, more specifically, to increasing the permeability of propped fractures that are formed during hydraulic fracturing of subterranean formations.
U.S. Pat. No. 6,725,930 describes an underground formation hydraulic fracturing method wherein at least part of the fracture is filled with a proppant material in the form of elongated particles, which may be in the form of segments of metallic wire, with a maximum to minimum dimension ratio of more than 5. The rest of the fracture is filled with standard non-metallic proppant. The fracture permeability increases as a result.
In U.S. Pat. No. 6,059,034, an underground formation is treated by filling a fracture with a proppant material and deformed particles. The deformed particles can be combined with the proppant for increasing fracture permeability, reducing the production of fine grained particles and/or reduction of proppant backflow. The material used for hydraulic fracturing can be sand, and the deformed particles can be polystyrene divinylbenzene beads.
U.S. Pat. No. 5,908,073 describes an underground formation fracture propping method wherein proppant backflow from the fracture is prevented simultaneously. The method is based on the use of a mixture of fibrous bundles and proppant for filling the fracture when the fracture remains open and then the fracture is allowed to close on the proppant and fiber mixture. According to this patent, proppant backflow is prevented due to the use of the fiber bundles consisting of 5 to 200 separate fibers, the length of which ranges from 0.8 to 2.5 mm and the diameter of which ranges from 10 to 1000 μm.
The addition of fibers or fiber-like structures to the product can contribute to the reduction of proppant backflow and simultaneously increase the density of proppant packing in the fracture. Also the fibers reduce the migration of fine grained proppant and thus prevent the reduction of proppant packing permeability in the fracture, though not completely.
In U.S. Pat. No. 5,330,005, a method of controlling proppant backflow from an underground formation is disclosed wherein the addition of fiber materials to the mixture used for hydraulic fracturing and to the well gravel-packed filter reduces proppant backflow and/or the production of fine grained grit in the packing, thus stabilizing the packing and reducing the consumption of high polymer fluids. The preferable materials for the fibers are glass, aramid, nylon and other natural or synthetic organic and inorganic fibers and metallic wires.
A method wherein the underground formation is processed by pumping a mixture of standard proppant and deformed material particles into the formation is described in U.S. Pat. No. 6,330,916. The deformed material particles can be combined with standard proppant for increasing the permeability, reducing the production of fine grained proppant grit and/or reducing proppant backflow. The propping agent can be a material such as sand, and the deformed particles can be a material such as polystyrene divinylbenzene beads. Also this patent discusses the possibility of using natural materials such as nutshells, seeds, fruit seeds and processed wood. However, natural materials can add an extra amount of fine grained material to the packing and thus reduce the permeability.